Polycarbonate resins are excellent in transparency, impact resistance, heat resistance and the like, and in addition, molded products obtained therefrom are excellent in size stability and the like. For this reason, polycarbonate resins are widely used as raw material resins for the production of housings of electrical and electronic equipments, automobile parts, and precision molded products such as parts related to optical disks. In particular, as cases of home appliances, electronic equipments and image display devices, etc., products having high commercial value can be obtained, taking advantage of beautiful outer appearance thereof. Further, reinforced polycarbonate resins, in which various inorganic fillers are added to polycarbonate resins, are also used for a wide range of purposes because of excellent mechanical strength and heat resistance thereof.
Recently, reduction in size and thickness of electronic equipments including information/mobile devices as described above has been accelerated. For this reason, as a material to be used, a sheet/film having excellent mechanical properties and good flame retardance even in the case where the thickness thereof is reduced has been desired.
In particular, the size and thickness of cases of electrical and electronic equipments, etc. have been extremely reduced because of tendency of reduction in size of such equipments themselves. For this reason, high flame retardance, for example, V-1 or higher in the UL94 vertical burning test even in the case where the thickness is 0.8 mm or less, has been desired.
When preparing such a thin-walled molded product, an extrusion molding machine including sheet/film molding is more advantageous than an injection molding machine. In particular, when an inorganic filler is contained for the improvement of mechanical properties, since the flowability of a resin composition is reduced, it is difficult to perform large-area molding with a thickness of 0.8 mm or less by means of injection molding. Further, when employing a multiple gate for large-area molding, problems such as reduction in properties and poor outer appearance are caused by a weld. Meanwhile, extrusion-molded products do not have these problems because the range of the flowability appropriate for molding is different from that of injection-molded products, and therefore it is possible to perform large-area molding continuously.
Patent Document 1 describes a polycarbonate resin composition, wherein a glass fiber is used as an inorganic filler and a metal salt-based flame retardant or organic phosphorus-based flame retardant is used as a flame retardant. Patent Document 1 describes that the viscosity average molecular weight of polycarbonate resin is particularly preferably 14,000 to 24,000, and in the Examples, the viscosity average molecular weight is 22,400, and flame retardance is V-0 in the case where the thickness is 0.8 mm or 1.6 mm. Patent Document 2 describes a polycarbonate resin composition, wherein a glass fiber is used as an inorganic filler and a phosphazene compound is used as a flame retardant. Patent Document 2 describes that the viscosity average molecular weight of polycarbonate resin is particularly preferably 17,000 to 24,000, and in the Examples, the viscosity average molecular weight is 21,000, and flame retardance is V-0 in the case where the thickness is 1.0 mm.
However, in the case of the compositions described in Patent Documents 1 and 2, flame retardance is insufficient when a molded product has a smaller thickness. Moreover, since these are flame-retardant polycarbonate resin compositions to be used for injection molding, it is difficult to obtain a thin-walled film/sheet having a large area.
Patent Document 3 describes a polycarbonate resin composition for extrusion molding. Patent Document 3 describes that the viscosity-average molecular weight is particularly preferably 17,000 to 28,000, and in the Examples, flame retardance is V-0 in the case where the thickness is 0.5 mm.
However, since the composition described in Patent Document 3 does not contain an inorganic filler, sufficient bending characteristics cannot be obtained, and mechanical strength is insufficient.